Keyboard expression
Keyboard expression is the ability of a keyboard musical instrument to change tone or other qualities of the sound in response to velocity, pressure or other variations in how the performer depresses the keys of the musical keyboard. Expression types include:
Keyboard instruments offer a range of expression types. Acoustic pianos, such as upright and grand pianos, are velocity-sensitive—the faster the key strike, the harder the hammer hits the strings. Baroque-style clavichords and professional synthesizers are aftertouch-sensitive—applied force on the key after the initial strike produces effects such as vibrato or swells in volume. Tracker pipe organs and some electronic organs are displacement-sensitive—partly depressing a key produces a quieter tone.
Other types[edit]
Acoustic pianos have expression pedals that change the response or tone of the instrument.
On small upright pianos, the soft pedal (also called una corda or half-blow pedal) moves the hammers closer to the strings. On grand pianos, the soft pedal moves the hammers sideways so each hammer strikes only part of its string group.
The sustain pedal (also called damper pedal) prevents individual key dampers from lifting when the player releases the key. All notes played with the sustain pedal ring until the player releases the sustain pedal (or until the note completely decays). With the dampers not applied, octave, fifth, and other overtones vibrate sympathetically, producing a richer sound. Most electronic keyboards also have a sustain pedal that holds notes and chords, but only high-end digital keyboards reproduce the sympathetic vibration effect.
Electromechanical keyboards and electronic keyboards offer a range of other expression devices. Electromechanical keyboards such as the Hammond organ offer additional means of keyboard expression by modifying the starting, stopping, or speed of the rotating Leslie speaker or by engaging a variety of vibrato or chorus effects. Digital "clones" of Hammond organs offer recreations of these effects, along with other effects. The VK-9 digital organ, for example, offers a proximity-sensitive detector that triggers the Leslie speaker, a ring modulator, or other effects.
Some effect pedals used with electromechanical keyboards such as the Fender Rhodes electric piano or digital keyboards respond to loudness and so, indirectly, to key velocity. Examples include overdrive pedals, which produce a clean sound for softer notes, and a distortion effect for louder notes—and fixed wah-wah pedals that filter the audio signal based on loudness.